Cold surface pavement planers have been used to scarify and profile concrete and asphaltic pavements. To accomplish this function, a movable chassis supports a rotatable cutter drum. An engine on the chassis is used to drive the cutter drum as well as move the chassis and power other auxiliaries. To reduce the speed of the engine and provide power for the cutter drum, a gear box is located within the drum, and a coupling provided between the engine and the gear box.
Since the cutter drum must rotate slowly, a substantial reduction in speed is provided by the gear box, and the power losses in the gear box, which operates at an efficiency of about 90%, cause considerable heating of the box.
In the past, the surfaces of the gear box exposed to air in the drum dissipated heat by means of convection into the air, and then through the drum surface. This inefficient heat transfer caused significant heating problems and often overheating of the gear box.